This invention relates generally to filter cartridges and more particularly to filter cartridges having integrated filtration elements.
Filter cartridges typically comprise a porous filtration element disposed within a structural housing. In such filters, unfiltered fluid enters the housing through an inlet port and passes through the filtration element, which removes contaminants or other impurities from the fluid. The filtered fluid is discharged through an outlet port. Filter cartridges include so-called “quick change” cartridges that typically have the inlet and outlet combined in a single port at one end of the housing and in-line cartridges in which the inlet and outlet ports are located at opposite ends of the housing. Because the fluid flow is often pressurized, these ports are typically sealed, such as with an O-ring or the like. It is therefore desirable to provide small ports because larger openings are more difficult to seal (the larger the seal, the larger the force it is subjected to for a given pressure). Accordingly, the ports are typically smaller in cross dimension than the interior of the housing that contains the filtration element.
It is known to use a bed of granular filtration media, such as powdered activated carbon, activated alumina, silica, zeolites and the like, as the filtration element. (As used herein, the term “granular” is intended to encompass any material in a divided state; that is, material comprising separate particles that easily move and change their relative position without a separation of the mass and that are generally capable of flowing. The term “particle” refers to any relatively small, discrete portion or piece of something and includes grains, granules, particles, pellets, fibers and the like.) A granular filtration media can be poured into the housing interior through the small port. Suitable materials can be added to lightly compress the filtration media so that it is held in a semi-compact arrangement. However, because there is little or no cohesion within the granular filtration media, such filter systems can experience redistribution of the media particles and channeling (i.e., filtrate flowing through the bed of granular material in preferential flow paths, instead of a uniform flow distribution). This can result in a decreased filtration quality. Filter systems employing loose filtration media can also suffer from poor filtration efficiency.
A common solution to these drawbacks has been the advent of compacted filtration media that are molded or extruded into a stable shape, using a suitable glue or binder, which is typically fused by heating. Advances in polymer sintering have allowed suitable filtration elements to be produced by gently dispensing a mixture of a granular filtration media and powdered polymers into a simple mold and heating to a prescribed temperature for a prescribed period of time to form a coherent, self-supporting porous matrix. Such stable-shape filtration elements, typically referred to as “filter blocks,” are very good at forcing all filtrate through a constant torturous path without channeling and can be made with very small and uniform porosity to improve filtration efficiency in the low-micron range.
Unfortunately, because of their rigid shape, filter blocks cannot be installed through small filter housing ports and require a large opening to install them into the structural housing. Consequently, the state of the art is a two-piece housing assembly comprising a first component that contains the filter block and a second component that closes the first component. In this arrangement, the first component (often referred to as the “can” or “sump”) must initially provide a sufficiently large opening to allow the coherent filter block to be installed. The first component is commonly configured as a generally cylindrical barrel closed at one end and open at the other end to provide the large opening through which the filter block is inserted. The filter block is then enclosed by the second component (frequently referred to as the “cap” or “head”), which is placed over the large opening and attached (such as by welding or threaded connection) to the first component.
While such filter cartridges provide excellent performance, the two-piece design can add to the material, fabrication and assembly costs. Accordingly, it would be desirable to have a filter cartridge that is easier and more cost effective to manufacture than current filter cartridges. Additionally, it is desirable to eliminate the metal molds for forming the filter blocks and instead, form the blocks directly by using the one-piece filter housing itself.